Open Access Nano Express

Analysis of p-Si macropore etching using FFT-impedance spectroscopy

Emmanuel Ossei-Wusu*, Jürgen Carstensen and Helmut Föll

Author Affiliations

Institute for Materials Science, Christian-Albrechts-University of Kiel, Kaiserstrasse 2, Kiel, 24143, Germany

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Nanoscale Research Letters 2012, 7:320  doi:10.1186/1556-276X-7-320

Published: 20 June 2012

Abstract

The dependence of the etch mechanism of lithographically seeded macropores in low-doped p-type silicon on water and hydrofluoric acid (HF) concentrations has been investigated. Using different HF concentrations (prepared from 48 and 73 wt.% HF) in organic electrolytes, the pore morphologies of etched samples have been related to in situ impedance spectra (IS) obtained by Fast Fourier Transform (FFT) technique. It will be shown that most of the data can be fitted with a simple equivalent circuit model. The model predicts that the HF concentration is responsible for the net silicon dissolution rate, while the dissolution rate selectivity at the pore tips and walls that ultimately enables pore etching depends on the water content. The ‘quality’ of the pores increases with decreasing water content in HF/organic electrolytes.

Keywords:
p-Si macropores; HF concentration; water content or concentration; organic electrolytes; impedance spectroscopy